Provided nothing crazy happens. I can't see Sony wanting to get butt-hurt again with astronomical unit costs and hardware that nobody knows how to use, and MS's strength will always be software rather than hardware.
There's also the question of whether the new engine is being designed for PS3/360 and will be upscaled for next gen, or if it was designed for next gen and is being downscaled for current gen...
Your guess is as good as mine really...
It depends how much work they would have been doing on the new engine in the background. I'd expect most of the modes to be in place, though there might be some streamlining for the first year. I'd expect to see Football Life, MLO, the training challenges, the community hubs, hopefully the editor in a full form.
I'd like to think stadia and teams are ok? The artwork is most likely done in such a way that they just need to work out how to port into the new engine, rather than all of their stadia work having to be restarted from scratch. Pretty much all games now create art at levels way beyond what the game can put out, so that they can use the shadow maps to give the illusion that the graphics are a lot more detailed than they are. For example Any game with a suit of armour nowadays will make light reflect off the curves very convincingly, as if the suit is curved, when actually it's still made of lots of straight lined polygons as in PS2 days. You can only tell when you look at the outline, not at the centre of the shape in question.
Besides which - lighting will probably do more for PES's stadia than anything else.
Whether online will be fine is anyone's guess. Hopefully they'd have designed a new engine with online in mind?